Publication Date

2013-07-26

Availability

Open access

Embargo Period

2015-07-26

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Physics (Arts and Sciences)

Date of Defense

2013-07-01

First Committee Member

Massimiliano Galeazzi

Second Committee Member

Joshua Cohn

Third Committee Member

Fulin Zuo

Fourth Committee Member

Maria Ribeiro Gomes

Abstract

In recent years, there has been huge improvement in microcalorimetric technology and its applications. Today’s cryogenic microcalorimeter technology can be used in a large scale experiment with excellent energy and time resolutions. Transition Edge Sensor (TES) microcalorimeters are being developed as imaging spectrometers for a wide range of applications including neutrino mass measurement. We are developing a source (163Ho) embedded TES microcalorimeter for neutrino mass measurement. Energy resolution, rise time of events, decay time, and read-out electronics must be considered carefully in designing a microcalorimeter for the application of neutrino mass experiments. Our research is particularly focused on the investigation of the properties of the 163Ho imbedded metallic absorber for the application of the Ho-neutrino mass experiment. In a microcalorimetric neutrino mass experiment using the radioactive decay of 163Ho, the radioactive material must be fully embedded in the microcalorimeter absorber. One option that is being investigated is to implant the radioactive isotope into a gold absorber, as gold is successfully used in other applications. However, knowing the thermal properties at the working temperature of microcalorimeters is critical for choosing the absorber material and for optimizing the detector performance. In particular, it is paramount to understand if implanting the radioactive material in gold changes its heat capacity. We used a bolometric technique to measure the heat capacity of gold films, implanted with various concentrations of holmium and erbium (a byproduct of the 163Ho fabrication), in the temperature range 70 mK to 300 mK. Our results show that the specific heat capacity of the gold films is not affected by the implant, making this a viable option for a future microcalorimeter holmium experiment. Furthermore, most chemical processes to extract the Ho-163 isotope and insert it into a detector absorber involve yttrium based compounds. Rather than using yttrium as an intermediate step in the isotope extraction procedure, the metal yttrium silicide (Y5Si3) is a possible candidate to use directly as an absorber material. We measured the heat capacity of small Yttrium Silicide (Y5Si3) sample in the temperature range 90mK?300mK, to verify if it could be used as an absorber in the fabrication of microcalorimeters. We also measured its resistivity from room temperature to 90 mK. Our result indicated that the heat capacity of Y5Si3 is larger than gold (often used as absorber material) by more than a factor of five in the working temperature range of TES microcalorimeter.

Keywords

Microcalorimeter; Holmium; MARE; Neutrino

Share

COinS